The Heat Is On

12-01-2003
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Laura Tangley

Skeptics who still doubt that human activities are heating up the planet may have trouble explaining away the most recent evidence: An analysis by an international team of scientists found that the Northern Hemisphere has been hotter since 1980 than at any time during the past two millennia. To reach the conclusion, published in Geophysical Research Letters, the researchers examined historical records from several countries and, for the period before such records exist, analyzed rings from the trunks of ancient trees and air bubbles trapped in 2,000-year-old ice cores from Antarctica and Greenland.